Nucleophilic Substitution Reaction Type

In organic chemistry, nucleophilic substitution reactions involve the replacement of a leaving group in a molecule with a nucleophile. Consider the following reaction:

R-X + Nu- → R-Nu + X-

Where R represents an alkyl group, X is a leaving group, and Nu- is a nucleophile. What type of nucleophilic substitution reaction occurs when a secondary alkyl halide reacts with a strong nucleophile?